The cost of introducing new chemical entities into systems has led many companies to search for alternative methods of drug administration. In the 1980s, a new class of drug dosage forms was developed to provide controlled topical administration of a drug at a predetermined rate. S. K. Chandrasekaran, J. E. Shaw in Control and Release of Bioactive Materials, (R. W. Baker, ed.) Academic Press, Inc., New York, 1980, p. 99. The present invention in the preferred embodiment is devoted to a novel drug delivery system.
Polyaphrons, as defined herein, are multi-phase systems. Basically, they consist of a disperse of suspended phase such as tiny droplets of between about 1.mu.m to 1 mm encased in a continuous phase.
Where an oil is used as the dispersed phase and water is the continuous phase (immiscible liquids), it has been discovered that a therapeutically active substance such as a plant growth regulator or drug may be dissolved in an acceptable carrier such as oil. The polyaphron is then placed in communication with a medium and the substance can be slowly released into the medium. Preferably, the release is the substance leaving the disperse phase and entering the medium. Alternatively, the disperse phase can migrate into the medium and the substance released or a combination of both. Such a medium could be the plant in a soil or hydrophonic system of another organism such as the human body. For topical applications, the aphron could be gelled by carrying out a solvent or suspension-type polymerization in the oil phase forming something similar to a "bandaid" for long-term and steady delivery of drugs (the substance).
Polyaphrons or biliquid foams are preferably created when the gas phase in a colloidal gas aphron is replaced by an immiscible liquid.
The invention broadly comprises forming a polyaphron, the polyaphron comprising at least two fluid phases; a first continuous phase and a second disperse phase. The dispersed phase carries a substance which can be transferred to another medium.